In the manufacture of semiconductor chips a silicon wafer or other substrate is exposed to a variety of different processes in different processing chambers. The chambers may expose the wafer to plasmas, chemical vapors, metals, laser etching, and various deposition and acid etching processes in order to form circuitry and other structures on the wafer, During these processes, the silicon wafer may be held in place by an electrostatic chuck (ESC), a carrier, a pedestal, or a variety of other structures. An ESC holds the wafer by generating an electrostatic field to clamp the back side of the wafer to a flat surface or puck surface of the chuck. Other carriers use vacuum pressure, adhesive or other techniques.
As fabrication techniques for plasma processing equipment advance, such as those designed to perform plasma etching of microelectronic devices and the like, the temperature of the wafer during processing becomes more important. ESCs have been designed to provide a particular thermal profile across the surface of the substrate, sometimes called a workpiece. ESCs have also been designed to precisely regulate the temperature of the workpiece.
ESCs use liquid cooling to absorb the plasma power heat and remove it from the chuck. An ESC may also use the liquid to heat the chuck. This allows for a wider process window under different process and plasma conditions. A heat exchanger is used to heat or cool the liquid before it is pumped through the chuck and then valves control the rate of flow and the mixture of hot and cold fluid that is pumped through the chuck. A more precise thermal performance allows for more precisely formed structures on the wafer.